A great-grandson of King Edward I, Courtenay studied law at the University of Oxford, where he became chancellor in 1367. He was subsequently consecrated bishop of Hereford, Herefordshire, in 1370 and then of London (1375), where he led a clerical party against the ecclesiastical reformer John Wycliffe. He became archbishop of Canterbury in 1381.

Courtenay’s leadership was vigorous. He defended the lower clergy against papal and royal taxation and held a council at Canterbury in 1382 that condemned Wycliffe, whose works Courtenay censured. He obtained Richard’s permission to imprison heretics (1382) and to seize heretical books (1388), bringing him into conflict with John of Gaunt, duke of Lancaster and Wycliffe’s protector. In November 1382 Courtenay assembled a convocation at Oxford, where he forced the academic Lollards (holders of certain religious tenets derived from Wycliffe’s teachings) into submission. He protested the second (1390) Statute of Provisors, which disapproved of ecclesiastical offices appointed by the pope; he condemned it as a restraint upon apostolic power and liberty.